This app has been released: https://portableapps.com/apps/accessibility/nvda-portable
Download NVDA Portable 2020.4 Dev Test 1 [24MB download / 122MB installed]
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I'm keen to get this officially released to help folks in need of a screen reader on the go. Please give this a test and report back. We could even expand this with other languages via translators if it's successful.
2020-06-06: 2020.4 Dev Test 1: Updated to latest release, custom code to detect locked DLLs on exit, ask the user whether to ignore, suggest closing affected apps, and offer to restart Windows Explorer to free them